The present invention disclosed herein relates to nitride semiconductor devices, and more particularly, to GaN semiconductor devices having a structure in which currents are vertically applied.
A GaN based compound semiconductor is a direct energy gap semiconductor, may control wavelengths from visible rays to ultraviolet rays, and has excellent properties such as high thermal and chemical stability, high electron mobility and a saturated electron velocity, and large energy bandgap compared to typical GaAs and InP based compound semiconductors. Based on such characteristics, the application of the GaN based compound semiconductor is being expanded to optical devices such as visible light-emitting diodes LEDs and laser diodes LDs, and electronic devices used for next-generation wireless communication and satellite systems requiring high output power and high frequency characteristics, in which the typical compound semiconductors have limit In particular, nitride semiconductors (AlxInyGa1-x-yN) containing aluminum (Al) are next-generation nitride semiconductor materials that have a high energy bandgap characteristic of 3.4 eV to 6.2 eV, may be manufactured as light-emitting devices in all ultraviolet ranges, and may be manufactured as electronic devices by 2D electron gases (2-DEG) when forming heterojunction structures with GaN such as AlGaN/GaN and InAlN/GaN structures.
The semiconductor devices may be classified into two types: vertical devices in which currents flow perpendicularly to a substrate, and lateral devices in which the currents flow horizontally to the substrate. Examples of the vertical devices, such as a vertical diffused MOS (VDMOS) and an insulated gate bipolar mode transistor (IGBT) are easy to deal with high currents because bulk currents flow. The vertical devices are frequently used for power semiconductors due to such advantages but they have a limitation in that a manufacturing process is complicated. On the contrary, the lateral devices have a limitation in that it is difficult to deal with high currents because currents laterally flow only on the surface of a channel layer, but the manufacturing process is relatively simple. Most of the currently manufactured CMOSs and GaAs or GaN based semiconductor devices are lateral devices.
Since the GaN material has a large energy bandgap and high electron mobility compared to competitors such as Si, GaAs and SiC materials, it is appropriate for applying to power semiconductor devices. Furthermore, the GaN material shows excellent characteristics in power density, backward breakdown field, and electron mobility and is recently encroaching on the main market of a power semiconductor technology, IGBT. However, due to the intrinsic limit of the lateral device that is difficult to deal with high currents, there is a big difficulty in commercializing the GaN power semiconductor.